I noticed the other day that there is a garage near me selling CNG. The garage mainly caters for trucks and the CNG is probably also for trucks or busses?

Anyway, it's currently at 27p/litre, so I started wondering if it's possible to use CNG on an LPG conversion, as it's essentially the same idea?

I know when natural gas came out years ago, people had to change the burners on all their hobs, but as the way the fuel is burnt in an engine is different, I wondered if there would be similar issues with CNG/LPG?

The manual for the Zavoli kit on my sisters Astra shows various gauge set ups for CNG.

So, can CNG be used on an LPG setup, or would changes need to be made?

CNG is made by compressing natural gas (which is mainly composed of methane [CH4]), to less than 1% of its volume at standard atmospheric pressure. It is stored and distributed in hard containers, at a normal pressure of 200–220 bar (2900–3200 psi), usually in cylindrical or spherical shapes.

I think there would be some major reworking needed to convert an LPG setup to CNG .... I suspect the tanks are different, the filler will be different, you'd have to take the vapouriser out and fit some sort of pressure reducing valve.

Quote:

CNG's volumetric energy density is estimated to be 42% of LNG's (because it is not liquefied), and 25% of diesel's.

For the same quantity you'd get less than 1/2 the range so the cost/per mile would be not far off the same ...

pressure on cng is far higher than on lpg, I have a pdf somewhere from opel showing the install on a Zafira. They have to have massive tanks so a custom multi tank setup is put in place of your original fuel tank and a tiny petrol tank is installed

I asked my installer whether he could fit that tank setup to my zafira and he said it was too much work with the valving and certification

I think the kindest thing to say about CNG is that it is currently where LPG was about 20-25 years ago:

- expensive to do the vehicle conversion
- no specialists available
- kits have to be imported
- very limited number of filling stations
- only really useful for fleet operators with their own filling facilities

With the very real difference that CNG is currently more expensive than LPG, so commercially it makes no sense, and hence there will be little or no market development of it.

Which is a bit of a shame, as it's RON is about 130, and so if you set up a turbocharged engine to use it, you can run absurd turbo pressures and get a remarkable amount of power from it! Even in a naturally aspirated engine you can run with compression ratios up to 15:1 and get very good thermal efficiency.

... but the absolute beauty of CNG is that it can be created from waste products not fossil fuel, and it's not just a carrier of energy like the hydrogen option. So.... create your methane from waste food or spent products (eg. from the dairy industry or sewage works), via anaerobic digestion, mess about with it a bit (compress & clean) to get a pure fuel, bottle it & sell. See organic-power & environment-agency.gov.uk/business/sectors
Meanwhile convert your vehicle, chilterngascars or greenconversions
or buy one greencarsite.co.uk/GREENCARS/Volvo-S60-CNG-Biofuel
.... Get a tank in your drive, fill it with methane-from-waste, add a vehicle filling system, eg. gasfill & voila, extremely low-carbon transport. Now I have to put my money where my mouth is!

The real attraction of this is that you can also use the gas to fuel your house boiler, almost-carbon-free home & transport PS. why are links switched off? It took me ages to insert them then I had to strip all the useful info!

I noticed the other day that there is a garage near me selling CNG. The garage mainly caters for trucks and the CNG is probably also for trucks or busses?

Anyway, it's currently at 27p/litre, so I started wondering if it's possible to use CNG on an LPG conversion, as it's essentially the same idea?

I know when natural gas came out years ago, people had to change the burners on all their hobs, but as the way the fuel is burnt in an engine is different, I wondered if there would be similar issues with CNG/LPG?

The manual for the Zavoli kit on my sisters Astra shows various gauge set ups for CNG.

So, can CNG be used on an LPG setup, or would changes need to be made?

There is very littel in terms of CNG filling stations in the UK. One in Nottingham ( I think) and one confirmed in Crewe. A whisper about oen proposed in Lincoln. Councils in Wiltshire I think run the Mayor's car on it. The trucks use LNG, not the same. There is an LNG network run by Chive. LNG is of no use for CNG powered vehicles. What one poster in theis threaed saw at 27p was LNG.

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